The present invention relates generally to an expansible anchor, and more particularly to an expansible anchor for securing an object to a support structure.
Expansible anchors of many different types are already known. The present invention is particularly concerned with the type in which an expansion anchor sleeve and an expander member are inserted into an expansion anchor hole formed in a support structure, and the screw which does not have a head and which extends through the sleeve and engages the expander member, has a portion extending out of the sleeve and through an opening in an object that is to be mounted on a support structure. One type of prior-art arrangement utilizes a nut that is threaded on that portion of the screw that extends outwardly beyond the object until the nut engages the outer surface of the object, bearing upon the same and pulling the screw in outward direction, so as to thereby expand the expansion anchor sleeve. Depending upon the hardness of the support structure in which the sleeve is being expanded, a relatively significant length of the screw may be pulled outwardly before the sleeve has been extended to the point where it is firmly anchored. This means that quite a substantial portion of the screw projects outwardly beyond the object being anchored, and also beyond the nut which holds the object in place on the screw. This is of course not only aesthetically unattractive, but also these projecting portions of the screws represent a significant potential source of accidents. In addition, the threads on these portions are exposed to ambient conditions, and may either be damaged by impact or may corrode, which makes it at least difficult and in some instances impossible to remove the screw so that the element which is being supported on the support structure, can be removed or replaced.
The prior art has proposed to overcome these disadvantages by using screws having heads, instead of employing nuts. In this case, the head itself eventually contacts the object being supported, as the screw is threaded into the sleeve, and when the head contacts the object, further turning of the screw will of course cause the expander member to be drawn into the expansion sleeve whereas no axial displacement of the screw can occur.
This solution overcomes the disadvantages of the type of construction described first, but it also eliminates a significant advantage offered by that type of construction. It is evident that in the first-mentioned construction, the respective expansion sleeve with the screw already threaded into the expander member and projecting out of the sleeve can be inserted into the respective expansion anchor hole and that the object to be mounted on the support structure can have holes predrilled or otherwise performed, which need merely be aligned with the respective screws so that the latter can be extended through them, whereupon the object is supported on the screws and need not be held in place while the nuts are threaded onto the respective outer ends of the respective screws. This is a significant advantage in terms of mounting the object, an advantage which is not offered by the second type of prior-art devices.
Heretofore, the art has not proposed any device of the type in question which eliminates the disadvantages of both prior-art approaches which have been outlined herebefore, and at the same time combines their advantages.